Electric power grids that carry electrical power to homes and businesses are sometimes prone to failure, resulting in a blackout for the affected areas. The causes for grid failure include imbalances between load and power generation.
Power grids are usually constantly monitored for alternating current (AC) frequency. Power grid operators try to keep the AC frequency as close to a fixed frequency as possible. For example, the nominal AC frequency of the power grid in the US is 60 Hz, while in Europe and parts of Japan, the nominal AC frequency of the power grid is 50 Hz. The overall accuracy of the AC frequency is such that most AC powered clocks use the AC power as their source of time increment.
While the AC frequency is nominally set at a certain value, the actual AC frequency drifts around the nominal value as a result of load and generation effects.
FIG. 1 shows an example of AC frequency vs. time. Power grid operators change the scheduled AC frequency 104 to deal with different parameters of the grid and to keep the overall average of the AC frequency at the nominal value. As seen in FIG. 1, the actual AC frequency 102 varies widely. An AC frequency error of ±0.02 Hz is well within the bounds of normal operation. The drift of the AC frequency, or drift frequency, refers to the deviation of the AC frequency from the nominal value. Typically, the drift frequency does not exceed 0.1 Hz in a stable system.
The monitoring of the AC frequency, however, usually does not reveal information that would indicate impending failure in the power grid until it is too late. Thus, there is a need for a power grid failure detection system that can warn operators of impeding failures or even automatically take emergency action.